Research On The Key Thechnology Of Optical Performance Monitoring In The High Speed Coherent Transmission System

Optical performance monitoring (OPM) is the key technology which guarantees the reliability and stability of optical network, and it provides an important reference for impairments equalization. The emerge of big data, cloud computation and online video not only brings about convenience to people’s production and life, but also puts forward higher demand of communication system and network flow. Due to the development of integrated circuit, high speed optical communication system has successfully entered100G era, and big telecommunication operators have also carried on a large scale deployment. Optical communication system of new generation mainly relies on the techniques of high-order modulation and multiplexing in the high speed coherent optical communication system. These new techniques improve spectrum efficiency and bring about new problems and challenges to OPM. To adapt the high speed coherent optical communication system and optical network, OPM technology needs to realize real time monitoring of multiple parameters such as optical power, optical channel wavelength, chromatic dispersion (CD), polarization mode dispersion (PMD), optical signal-to-noise ratio (OSNR) and nonlinear effects with high precision and large range.This thesis mainly focuses on the study of CD, OSNR and frequency offset monitoring methods in the high speed coherent optical system, and the main work is shown as follows:1. Monitoring methods of channel impairments such as CD, PMD and OSNR in the high speed coherent optical communication systems are analyzed and the advantages and weaknesses of the monitoring technologies are discussed and concluded. For the basic non-data-aided blind monitoring method and the data-aided training sequences monitoring method, theoretical analysis, formula deduction and system simulation are done, which gives the performance and complexity of monitoring.2. A data-aided method of joint CD and frequency offset estimation based on the training sequences is proposed. According to the channel transmission model, theoretical analysis and formula derivation are carried out. The monitoring performance of different kinds of training sequences and different length are discussed and validated by simulation. The simulation results show that the method is simple and applicable to multiple modulation formats, pulse shapers as well as various data rates. The proposed method achieves good accuracy and wide monitoring range, also it is verified to be robust to first-order PMD and OSNR.3. The OSNR monitoring technology based on the statistical moments in the coherent optical system is proposed. The relation of statistical moments of received signal and CD as well as OSNR in the transmission channel is deduced by formula. The feasibility of the method is also verified by Matlab simulation. The results show that the method can accurately monitor the OSNR in a certain range. The monitoring performance of OSNR is also analyzed when there exists large CD in the channel.